Microwave-assisted reconstruction of spent graphite and its enhanced energy-storage performance as LIB anodes

• Spent graphite from the end-of-life LIBs was modified by microwave irradiation. • Modified spent graphite as LIB anodes achieves a capacity of ≥ 400 mAh g –1 . • Microwave-irradiation in air leads to the formation of open sites in spent graphite. • 4. A suitable number of open sites are favorable in improving Li + -storage capacity. This paper reported a facile microwave-assisted process to modify spent graphite (SG) powders for their re-utilization as LIBs anodes. The SG powders were treated by a simple impurity-removal process and a microwave irradiation in air for an exposure time range of 15–40 s. The as-obtained samples were characterized via various techniques. The microwave-modified samples (MW-G) exhibit enlarged interlayer distances and some open sites in their layers. The results show that the microwave-irradiation time has an obvious effect on their energy-storage property, and too long irradiation is harmful for their performance. The sample (MW-G-15) with a microwave-irradiation time of 15 s displays a high specific capacity of ≥ 400 mAh g –1 , much higher than that (~300 mAh g –1 ) of the fresh commercially available graphite under the same test condition. MW-G-15 has a capacity retention of 96% and an initial coulombic efficiency (ICE) of 84%, and the charge transfer and rate capacities are highly improved. The enhanced performances of MW-G-15 are attributed to the reconstruction of graphite structure during the microwave irradiation by introducing suitable open sites or channels for the intercalation and migration of Li ions. This work gives a useful enlightenment to explore low-cost and eco-friendly approach towards re-utilization of spent graphite as LIBs anode materials.